April 25, 2011

Asian Carp and the Great Lakes Basin

As an avid fisherman in the Toledo, Ohio, area, I enjoy angling opportunities on the Maumee River and on Lake Erie. One of the most critical issues facing the Great Lakes region involves the migration of aquatic invasive species (AIS) such as the silver carp and bighead carp species, sometimes collectively referred to as the Asian carp. The common carp, a Eurasian species, was introduced into the U.S. in the early 19th century and was widely distributed by the U.S. government for use as a foodfish. These carp are thought to have a destructive impact on native species as they muddy the water and take out aquatic vegetation when rooting around in riverside mud banks. The Asian carp, with a similar destructive impact, have been spreading much more aggressively than the common carp in recent years.

Over the past several decades, silver, bighead, and grass carp have become well established in widening areas of the Mississippi River basin, which includes the Mississippi River and all of its tributaries. Silver and bighead carp are thought to have escaped aquaculture ponds along the Mississippi River during major flooding in the 1990s. Grass carp, on the other hand, have been well established in the Mississippi River since the 1970s.

Today, Bighead and silver carp are found in abundance throughout Mississippi River watersheds ranging from Louisiana to Ohio, while grass carp appear to be established primarily in the Texas watershed. U.S. Environmental Protection Agency researchers are extremely concerned about Asian carp reaching the Great Lakes Basin. To date, a limited number of bighead carp have been captured from Lake Erie, although no evidence shows them to have reproduced. Similarly, a limited number of grass carp and bighead carp have been caught in the Canadian portion of the Great Lakes, with no populations thought to be established there. In combating the threat posed by Asian carp on native fish throughout the Great Lakes Basin, the Army Corps of Engineers is developing a network of enhanced barriers and monitoring systems.

In addition, fish toxicants and increased commercial fishing and harvesting practices are being encouraged to reduce Asian carp populations. Unfortunately, researchers believe that Asian carp have recently breached an electric fish barrier on the Chicago Sanitary and Ship Canal. In June 2010, a 19-pound carp was discovered only a few miles downstream from Lake Michigan. To mitigate the threat posed by the Asian carp’s spread, the Obama Administration last December released a revised Asian Carp Control Strategy Framework for 2011, introducing 13 new initiatives as part of a comprehensive plan. While it is good to see bolstered efforts on this front, I question whether it will be enough, given the dramatic increase in Asian carp population and range these past few years.